It is a widely-employed method for measuring blood pressure of a living body to press a portion of the living body by a cuff, etc. to detect pressure oscillation waves (pulse waves) produced in synchronization with heartbeats of the living body and determine values of blood pressure of the living body based on a change in magnitude of the detected pressure oscillation waves.
However, the above-indicated blood pressure measuring method is not recommendable for application to such a living body, for example a patient after a surgical operation, whose blood pressure must be continuously monitored during a comparatively long period of time, because a portion of the living body is successively pressed during the period, thereby giving appreciable discomfort to the living body.